How do structural isomers differ from other isomers?

Answer 1

Structural isomers differ in their connectivity. Geometric isomers have the same connectivity, but differ in their geometry.

What do I mean by #"connectivity"#? Well, let's turn to organic chemistry, the which offers the richest source of isomerism.

Now given a simple formula of #C_4H_10#, I can write 2 structural isomers: #"n-butane, " H_3C-CH_2CH_2CH_3#, and #"isobutane " H_3C-CH(CH_3)CH_3#. Clearly these are isomeric, because they have the same chemical formula. These are structural isomers because their connectivity is manifestly different: we have a straight chain isomer, and a branched one. Of course, as the chain grows, the opportunity for structural isomerism is magnified.

On the other hand, geometric isomerism may be illustrated with #"2-butylene, "H_3C-CH=CHCH_3#, which can generate 2 geometric isomers as shown![https://useruploads.tutor.hix.org/5X7Gi0MESgaZUTYCojcq_butene_1.png) :

Looking at the isomers, clearly they have the same connectivity: #C1# connects to #C2#............#C4#. Nevertheless, because of the disposition of alkyl groups about the olefin, the isomers have distinct physical and chemical properties. These, we would classify as geometric isomers, given the disposition of alkyl groups about the olefinic bond.

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Answer 2

Addison Armstrong

Structural isomers have different structural arrangements of atoms, whereas other isomers share the same molecular formula but differ in other aspects like spatial arrangement (stereoisomers) or connectivity (constitutional isomers).

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.